Improving the Design of a Milli-Fluidic Device

            Through the course of my research this summer, I improved the design and fabrication of milli-fluidic devices as well as their ability to perform liquid-liquid extraction (LLE).
            Many chemical processes require a separation of resultant compounds in order to yield a specific product. For example, pharmaceutical companies rely on compound separation to recover pharmaceutical molecules from an organic environment by extracting them into an aqueous stream. Called liquid-liquid extraction, the process of transferring a solute from one liquid phase into another is based on the interaction and behavior of two immiscible fluids. Yet, LLE commonly occurs on a large scale, which can lead to low separation efficiency and low product yield due to incomplete separation of the two liquid phases. Some existing separation methods include evaporation, centrifugation, or filtration, but these techniques can degrade the molecule of interest and are susceptible to loss of product. For these reasons, LLE on a  milli-fluidic level is more appealing because it caters to the extraction of small volumes of costly solutes. Hence, a major objective of my summer research was to improve the design of existing milli-fluidic prototypes to boost the usefulness and appeal of using such devices.
            The design and fabrication of milli-fluidic devices at the start of my research were impractical and ineffective, resulting in unstable devices. The devices held too many components that could vary from device to device. Through my research, I improved the design of milli-fluidic devices by simplifying the manufacturing process and increasing their effectiveness. My efforts to accomplish this were centered on modifying the fabrication technique and materials of construction. Such modifications include replacing the needles in the device with larger diameter tubing and utilizing different diameter tubing throughout the device to control its internal pressure. I tested and compared device prototypes based on their ability to stabilize an aqueous/organic interface and separate an aqueous/organic emulsion.
            The construction of a milli-fluidic device involves using a laser cutter to print an acrylic top and bottom piece, in which the bottom piece contains two input channels, a larger fluid compartment where the aqueous/organic interface occurs, and two effluent channels. A needle is adhered to the upper left channel, 14-gage tubing in the upper right channel, and 18-gage tubing in the lower left and right channels. “Loctite Plastic Bonding System” adhesive is used to secure the tubing needles in the channels. The two acrylic pieces are then secured to each other with six screws, six nuts, and twelve washers. A PEG solution is injected into the fluid compartment, and ultraviolet light is used to cure a layer of PEG hydrogel inside of the device. Holding the device perpendicular to the ultraviolet light is crucial in forming a smooth layer, which is important in maintaining laminar flow within the device.
            Overall, the improvements I have made to the design and fabrication process of milli-fluidic devices has allowed for an increase in manufacturing efficiency, structural consistency between devices, and performance.